Stroke is the most prominent cause of permanent disability in the industrialized countries. One of the most prominent disabilities stroke survivors suffer from is half sided paralysis of the upper limbs. Rehabilitation exercises are proven to be efficient in regaining motor control, provided the training is intense and the patient is guided in the therapy.
Technical solutions for unsupervised home stroke rehabilitation require the use of appropriate feedback mechanisms to ensure proper exercising.
Motor skill acquisition in healthy persons as well as stroke victims is facilitated by so called ‘augmented’ or ‘external’ feedback. This type of feedback is in contrast to internal feedback where the person moving uses its own senses such as vision or proprioception.
External feedback can for example be given verbally through a coach. Such external feedback is for example known from sports teaching situations, e.g. when a person is taught how to make a golf stroke, or from physiotherapists, e.g. in case of stroke victims learning to reach out for an object again.
Another popular method especially in motor skill acquisition in sport is video analysis, as for example described in US 2003/0054327, where the learner and/or a supervisor view the learner after having executed a prescribed motion.
As video analysis captures only a single movement plane, inertial sensor systems are becoming increasingly popular.
Inertial sensors capture linear acceleration, angular velocity, and magnetic fields and can be used for a 3-dimensional motion capture of all limbs they are attached to.
The motion data is displayed to the learner in form of a rendered, animated figure, a so-called avatar. A coach is providing cues to the learners to point their attention to mistakes in the motion execution when reviewing the avatar motion with them.
An unsupervised home-stroke rehabilitation equipped with inertial sensors is able to track the movements of a patient in the 3D space. The resulting data provides the basis to render an avatar that mimics the movements of the patient. Both, the patient and/or the therapist can watch the avatar to analyze the patient's movements. Since the sensor system provides 3D data, the system enables the reviewer to watch the movements from different angles by rotating the avatar on the screen.
A problem experienced with the existing external feedback systems is that the viewing configuration, i.e. the rotation, tilt, zoom, and eventual other parameters, is still to be determined by the patient or the therapist, or in case of a sports teaching situation, by the trainee or the coach.
Current research prototypes of home-stroke rehabilitation systems using inertial sensors show the recorded movements from a pre-selected angle. This viewpoint is pre-selected to allow for the ‘best’ evaluation of the recorded movement.
However, the 3-dimensional recorded data allows the viewer to view the movements from different angles. A known system allows the viewer to rotate the avatar or zoom into the figure while watching the recordings, as shown in FIGS. 1 and 2. However, in this known system, the viewer still needs to be aware about the best viewport or, in other systems, the viewer is restricted to certain, pre-defined viewing setups that can be selected on demand. Thus, the viewer has to select the optimal configuration for reviewing the recorded data.
Since patients usually lack the expertise and additionally are cognitively impaired, they are in general not able to select the optimal viewing configuration. The optimal viewing configuration assists the patients in analyzing their own movements and recognizing wrong movement patterns.
For the therapists, selecting the optimal viewing configuration might require repeated watching of the exercises. Thus, starting with a viewing setup targeting at the problematic elements of the movement would increase the efficiency in the therapist's review process.
This also shows the benefit of measuring 3D motion data compared to 2D recordings, as for example delivered by a video camera. The 3D data allows the viewer to ‘walk around’ the virtual representation of the patient and focus on the region of interest.
Existing systems allow the user only to manually choose the viewing direction in steps of 90 degrees.
The present invention describes a method for determining a viewing configuration of a rendered figure of a rehab-patient, aiming to deliver a suitable view on the rendered figure.